Molecular mapping of a male sterile gene (ms30) in maize
--Liang, Y, Zhou, H, Jiang, W

Professor Li Jingxiong found a male sterile gene (his designation is msx) and located it on maize chromosome 4 with B-A translocations (unpublished data). Dr. Zhou Hongsheng (1997) studied microspore development and found that pollen in Msx msx was normal, but that the msx msx anther was abnormal from the uninucleate stage. They thought it was a new male sterile gene and temporarily named it ms30 in the book "Biology of Male Sterility in Maize" (Li Jingxiong et al., 1998). Professor Li gave some seeds to M. C. Albertsen who tested the gene and published a paper in MNL71. In his paper, Dr. Albertsen designated the gene as ms*-li89. In last year's MNL72, Dr. Albertsen has designated an ms mutant ms*-WL87A on 2L as ms30 (see MNL72:38). So, we have the same name for different mutants. How to resolve the problem?

We mapped ms30 by RFLP and RAPD markers in this report. A BC1 population derived from 6960 (ms30 ms30) X Zhonghuang17 (Ms30 Ms30) and a sibling population SIB5(((2603SuSu ms30 ms30/2611susu Ms30 Ms30)F2)SIB5) were employed as map populations for RFLP analysis, while the BC1 was used for RAPD analysis. Eighteen probes on maize chromosome 4 and BSA analysis were used to screen with RFLPs, 278 10-mer random primers and BSA analysis were employed to identify RAPDs. By using JoinMap software, linkage as well as genetic distance between ms30 and markers were obtained. As a result, ms30 was mapped on chromosome 4. The main results were as follows:

1. Observing anthers at the flowering period, we found that 71 plants were sterile while 64 plants were fertile among 135 individuals in the SIB5, and 64 plants were sterile while 57 plants were fertile among 120 individuals in the BC1. Thus the ratio of sterility to fertility conformed to the expected ratio 1:1.

2. RFLP analysis on the SIB5 population showed that ms30 was tightly linked with two RFLP loci umc15a and umc66a on maize 4L, the recombination value was 5.9% and 14.8% respectively.

3. In the BC1 population, polymorphism was detected between parents and between two bulked DNA pools by the probes umc66a, umc19, umc15a, bnl7.65, csu178a and csu91a. While umc19, umc15a, bnl7.65, csu178a were used to conduct further analysis on BC1 individuals. Results showed that ms30 was tightly linked to them, the genetic distance was umc19-14cM-Ms30/ms30 -4.2cM-umc15a-1.4cM-bnl7.65-3.4cM-csu178a (see Figure).

4. In RAPD analysis, a RAPD marker (RAPDK19-1.4) was found to be tightly linked to ms30. The genetic distance was 2.6cM.

Results from RFLP analysis on two different segregating populations strongly supported that ms30 was on maize 4L, which was in accordance with the previous study by the B-A system. Because two known male sterile genes on chromosome 4 are dominant, therefore the recessive male sterile gene ms30 is a new ms gene.


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